Use canonical capitalization of Unicode-3.0 SPDX tag

The SPDX database lists the license as 'Unicode-3.0', and 'Unicode
License v3'. Now, the SPDX standard actually says that

   License identifiers (including license exception identifiers) used
   in SPDX documents or source code files should be matched in a case-
   insensitive manner.

But the website at https://spdx.org/licenses/ doesn't treat it this way,
so the link we generate out of the identifier actually gives a 404. So
it's just easier to use the 'original' capitalization.

Amends 063026cc503

Pick-to: 6.5 6.6 6.7
Change-Id: I826077a914721b7b9499ad62c08fdf20be94e88d
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

src/corelib/text/qt_attribution.json

@@ -35,8 +35,8 @@
  available.",
     "Homepage": "https://cldr.unicode.org/",
     "Version": "v44.1",
-    "License": "Unicode License V3",
-    "LicenseId": "UNICODE-3.0",
+    "License": "Unicode License v3",
+    "LicenseId": "Unicode-3.0",
     "Copyright": "Copyright (C) 2004-2023 Unicode, Inc."
 }
 ]